I'm not 100% certain...but that might actually be the hat from the Gem Store Pirate Costume. I haven't checked the costumes out myself but a guildmate bought the costume and the hat looks very similar. You can do a preview of the costume on your character in the Gem Store without having to purchase to check if it's the one

That "Pirate" set is the generic medium armor set that seems to drop just about everywhere from mid-level until 80, where I still get it constantly as drops while farming in Cursed Shore. Once you get higher level, you probably won't even be able to avoid it.